Semiconductor device structure and methods of forming the same

ABSTRACT

A semiconductor device structure, along with methods of forming such, are described. The structure includes a substrate having one or more devices formed thereon, one or more bonding pads disposed over the substrate, and a first passivation layer disposed over the one or more bonding pads. The first passivation layer includes a first passivation sublayer having a first dielectric material, a second passivation sublayer disposed over the first passivation sublayer, and the second passivation sublayer has a second dielectric material different from the first dielectric material. The first passivation layer further includes a third passivation sublayer disposed over the second passivation sublayer, and the third passivation sublayer has a third dielectric material different from the second dielectric material. At least two of the first, second, and third passivation sublayers each includes a nitride.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/917,640 filed Jun. 30, 2020, which is incorporated byreference in its entirety.

BACKGROUND

In the formation of integrated circuits, devices such as transistors areformed on a semiconductor substrate. An interconnection structure isthen formed over the integrated circuit devices. A redistribution layer(RDL) is formed over the interconnection structure. The RDL includes atleast a conductive feature and a passivation layer, and the conductivefeature is electrically connected to the interconnection structure. Thepassivation layer is formed over the conductive feature.

However, the different materials in the RDL may have differentcoefficients of thermal expansion. The coefficient of thermal expansionmismatch in the RDL leads to the formation of cracks extending from theRDL to the interconnection structure, which can cause device failure.Therefore, there is a need to solve the above problems.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a cross-sectional side view of a semiconductor devicestructure, in accordance with some embodiments.

FIG. 2 is a flowchart of a method for fabricating the semiconductordevice structure, in accordance with some embodiments.

FIGS. 3A and 3B are cross-sectional side views of a redistribution layerat one stage during fabrication of the semiconductor device structure ofFIG. 1, in accordance with some embodiments.

FIG. 4 is a flowchart of a method for fabricating the redistributionlayer of the semiconductor device structure of FIG. 1, in accordancewith some embodiments.

FIGS. 5A-5I illustrate cross-sectional side views of the redistributionlayer during various fabrication stages of the method of FIG. 4, inaccordance with some embodiments.

FIG. 6A is a cross-sectional side view of a passivation layer disposedover a plurality of conductive features, in accordance with someembodiments.

FIG. 6B is a top view of the plurality of the conductive features ofFIG. 6A, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “over,” “on,” “top,” “upper” and the like, may be used hereinfor ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. The spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

FIG. 1 is a cross-sectional side view of a semiconductor devicestructure 100, in accordance with some embodiments. FIG. 2 is aflowchart of a method 200 for fabricating the semiconductor devicestructure 100, in accordance with some embodiments. The semiconductordevice structure 100 and the method 200 making the same are collectivelydescribed with reference to FIGS. 1 and 2. The semiconductor devicestructure 100 may be an integrated circuit (IC) structure having aplurality of IC devices, such as transistors, diodes, sensors, memorycells, or combinations thereof.

The semiconductor device structure 100 includes a substrate 102. Thesubstrate 102 may be a semiconductor substrate, such as a bulk siliconsubstrate. In some embodiments, the substrate 102 may be an elementarysemiconductor, such as silicon or germanium in a crystalline structure;a compound semiconductor, such as silicon germanium, silicon carbide,gallium arsenic, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide; other suitable materials; or combinationsthereof. Possible substrates 102 also include a silicon-on-insulator(SOI) substrate. SOI substrates are fabricated using separation byimplantation of oxygen (SIMOX), wafer bonding, and/or other suitablemethods.

The substrate 102 also includes various isolation features, such asisolation features 104 formed on the substrate 102 and defining variousactive regions 106 on the substrate 102. The isolation feature 104utilizes isolation technology, such as shallow trench isolation (STI),to define and electrically isolate the various active regions 106. Theisolation feature 104 may be made of silicon oxide, silicon nitride,silicon oxynitride, other suitable dielectric materials, or combinationsthereof. The isolation feature 104 is formed by any suitable process. Asone example, forming STI features includes a lithography process toexpose a portion of the substrate 102, etching a trench in the exposedportion of the substrate 102 (for example, by using a dry etching and/orwet etching), filling the trench (for example, by using a chemical vapordeposition process) with one or more dielectric materials, andplanarizing the substrate 102 and removing excessive portions of thedielectric material(s) by a polishing process, such as a chemicalmechanical polishing (CMP) process. In some examples, the filled trenchmay have a multi-layer structure, such as a thermal oxide liner layerand filling layer of silicon oxide.

The active region 106 is a region having various features that are partsof one or more devices 110, such as transistors, diodes, imagingsensors, resistors, capacitors, inductors, memory cells, a combinationthereof, and/or other suitable devices. The active region 106 mayinclude a semiconductor material similar to that of the bulksemiconductor material of the substrate 102 (such as silicon) ordifferent semiconductor material, such as silicon germanium, siliconcarbide, or multiple semiconductor material layers (such as alternativesilicon and silicon germanium layers) formed on the substrate 102 byepitaxial growth, for performance enhancement, such as strain effect toincrease carrier mobility. In some embodiments, the active region 106 isthree-dimensional, and the devices 110 in the active region 106 may bethree-dimensional devices, such as fin field-effect transistors(FinFETs), nanosheet transistors, or other suitable three-dimensionaldevices.

The substrate 102 may include various doped features, such as n-typedoped wells, p-type doped wells, source and drain, other doped features,or a combination thereof configured to form various devices 110 orcomponents of the devices 110.

The semiconductor device structure 100 further includes aninterconnection structure 120 formed on the substrate 102, such as onthe active regions 106 and the isolation features 104. Theinterconnection structure 120 includes various conductive features, suchas a first plurality of conductive features 124 and second plurality ofconductive features 126, and an interlayer dielectric (ILD) 122 toseparate and isolate various conductive features 124, 126. In someembodiments, the first plurality of conductive features 124 areconductive vias and the second plurality of conductive features 126 areconductive lines. The interconnection structure 120 includes multiplelevels of the conductive features 126, and the conductive features 126are arranged in each level to provide electrical paths to variousdevices 110 disposed below. The conductive features 124 provide verticalelectrical routing from the substrate 102 to the conductive features 126and between conductive features 126. The conductive features 124 andconductive features 126 may be made from one or more conductivematerials, such as metal, metal alloy, metal nitride, or silicide. Forexample, the conductive features 124 and the conductive features 126 aremade from copper, aluminum, aluminum copper alloy, titanium, titaniumnitride, tantalum, tantalum nitride, titanium silicon nitride,zirconium, gold, silver, cobalt, nickel, tungsten, tungsten nitride,tungsten silicon nitride, platinum, chromium, molybdenum, hafnium, othersuitable conductive material, or a combination thereof. Conductivecontacts (not shown) may be formed between the devices 110 and theconductive features 124, and the conductive contacts may be made fromtungsten, silicide, nickel, cobalt, copper, other suitable conductivematerial, or a combination thereof.

The ILD 122 includes one or more dielectric materials to provideisolation functions to various device components (such as gates) andvarious conductive features (such as conductive lines, vias, andcontacts). The ILD 122 may include multiple dielectric layers embeddingmultiple levels of conductive features 124, 126. The ILD 122 is madefrom a dielectric material, such as silicon oxide, a low-k dielectricmaterial, other suitable dielectric material, or a combination thereof.In some examples, the low-k dielectric material includes fluorinatedsilica glass, carbon doped silicon oxide, xerogel, aerogel, amorphousfluorinated carbon, Parylene, bis-benzocyclobutenes, polyimide, and/orother suitable dielectric materials with dielectric constantsubstantially less than that of the thermal silicon oxide. In someembodiments, the ILD 122 includes silicon oxide, silicon oxycarbide, oneor more porous low-k dielectric materials, borophosphosilicate glass,phosphosilicate glass, boron silicate glass, silicon nitride, siliconoxynitride, silicon oxycarbon nitride, high density plasma oxide formedby a high density plasma chemical vapor deposition (HDP-CVD) process orother suitable processes, spin on glass, polyimide, other suitablematerials, or a combination thereof. The formation of the ILD 122includes deposition and CMP processes, for example. The deposition mayinclude spin-on coating, chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), HDP-CVD, other suitabledeposition technology, or a combination thereof. The ILD 122 may includemultiple layers and is collectively formed with various conductivefeatures in a proper procedure, such as damascene process.

In some embodiments, the interconnection structure 120 or a portionthereof is formed by deposition and patterning. For example, aconductive material, such as aluminum copper, is deposited by physicalvapor deposition (PVD), then is patterned by lithography and etchingprocesses. The ILD 122 is then formed on the aluminum copper by adeposition process, such as CVD or PECVD. In some embodiments, theconductive features 124, 126 are formed by a damascene process. A dualdamascene process may be performed to form one level of the conductivefeature 126 and the conductive feature 124 below the conductive feature126.

The semiconductor device structure 100 further includes a redistributionlayer (RDL) 140 disposed on the interconnection structure 120 toredistribute bonding pads. The RDL 140 helps to arrange the bondingpads, such as from the edge to the center of an IC chip for flip chipbonding or other suitable packaging technology to integrate an IC chipto a board (e.g., a printed circuit board).

The RDL 140 includes one or more passivation layers and conductivefeatures formed in the one or more passivation layers. In someembodiments, the RDL 140 includes a first passivation layer 144 and asecond passivation layer 146 disposed on the first passivation layer144. The first passivation layer 144 may be a single layer of adielectric material, such as silicon oxide, silicon oxycarbide, one ormore porous low-k dielectric materials, undoped silica glass,borophosphosilicate glass, phosphosilicate glass, boron silicate glass,silicon nitride, silicon oxynitride, silicon oxycarbon nitride, highdensity plasma oxide formed by a HDP-CVD process or other suitableprocesses, spin on glass, polyimide, other suitable materials, or acombination thereof. In some embodiments, the first passivation layer144 includes a multi-layer stack of dielectric materials. For example,the first passivation layer 144 may include a silicon nitride layer andan un-doped silica glass layer disposed on the silicon nitride layer.Other configurations of the first passivation layer 144 are within thescope of the disclosure. The second passivation layer 146 includes amulti-layer stack of dielectric materials, and the second passivationlayer 146 is further described in detail below.

The RDL 140 includes conductive features 150 and conductive features152. The conductive features 150 may be conductive vias and theconductive features 152 may be bonding pads. In some embodiments, asshown in FIG. 1, one or more conductive features 150 may be disposed inthe first passivation layer 144, and the conductive features 150 may bealigned and in contact with corresponding conductive features 126located at the top of the interconnection structure 120. One or moreconductive features 152 may be disposed on the corresponding conductivefeatures 150 located in the first passivation layer 144. The secondpassivation layer 146 may be disposed on the conductive features 152 andthe first passivation layer 144.

One or more under bump metallurgy (UBM) layers 154 are disposed in thesecond passivation layer 146 and are in contact with correspondingconductive features 152. A conductive structure 156 is formed on eachUBM layer 154. The UBM layer 154 is made from a conductive material,such as copper, aluminum, tungsten, titanium, tantalum, other suitableconductive materials, alloys thereof, or a combination thereof. The UBMlayer 154 may contain an adhesion layer and/or a wetting layer. In someembodiments, the UBM layer 154 further includes a seed layer. Theconductive structure 156 may be a ball-like bump or a pillar. Theconductive structure 156 is made from a conductive material, such astin, copper, gold, silver, alloys thereof, other suitable materials, ora combination thereof.

FIG. 2 is a flowchart of a method 200 for making the semiconductordevice structure 100 in accordance with some embodiments. Somefabrication details are provided above and are not repeated here. Themethod 200 starts at operation 202 to form a plurality of devices 110 onthe substrate 102. The isolation features 104 may be already formed onthe substrate 102. At operation 204, the interconnection structure 120is formed over the plurality of devices 110. The RDL 140 is formed overthe interconnection structure 120, at operation 206. The RDL 140includes the passivation layer 146 which can reduce the formation ofcracks in the passivation layer 146 and/or confine the cracks within thepassivation layer 146. The method 200 may include other operationsbefore, during or after the above operations. The method to form the RDL140 is described in detail below.

FIG. 3A is a cross-sectional side view of the RDL 140 at one stageduring fabrication of the semiconductor device structure 100 of FIG. 1,in accordance with some embodiments. As shown in FIG. 3A, in someembodiments, the RDL 140 includes the first passivation layer 144 havinga first passivation sublayer 144A and a second passivation sublayer 144Bdisposed on the first passivation sublayer 144A. The first passivationsublayer 144A is made from a dielectric material, such as silicon oxide,silicon oxycarbide, one or more porous low-k dielectric materials,undoped silica glass, borophosphosilicate glass, phosphosilicate glass,boron silicate glass, silicon nitride, silicon oxynitride, siliconoxycarbon nitride, high density plasma oxide formed by HDP-CVD processor other suitable processes, spin on glass, polyimide, other suitablematerials, or a combination thereof. The second passivation sublayer144B is made from a dielectric material, such as silicon oxide, siliconoxycarbide, one or more porous low-k dielectric materials, undopedsilica glass, borophosphosilicate glass, phosphosilicate glass, boronsilicate glass, silicon nitride, silicon oxynitride, silicon oxycarbonnitride, high density plasma oxide formed by HDP-CVD process or othersuitable processes, spin on glass, or polyimide. The dielectric materialof the second passivation sublayer 144B is different from the dielectricmaterial of the first passivation sublayer 144A. In one embodiment, thefirst passivation sublayer 144A is silicon nitride, and the secondpassivation sublayer 144B is undoped silica glass. Other configurationsof the first passivation layer 144 are within the scope of thedisclosure. The first passivation sublayer 144A has a thickness T1ranging from about 50 nanometers (nm) to about 100 nm. The secondpassivation sublayer 144B has a thickness T2 ranging from about 500 nmto about 1000 nm.

The conductive features 150 are disposed in the first passivationsublayer 144A and the second passivation sublayer 144B. The conductivefeatures 150 extend through the first passivation sublayer 144A and thesecond passivation sublayer 144B. The conductive features 152 aredisposed on corresponding conductive features 150. The secondpassivation layer 146 is disposed on the first passivation layer 144 andthe conductive features 152. Due to the coefficient of thermal expansionmismatch between the conductive features 152 and the dielectricmaterials in the RDL 140, tensile stress is induced in the conductivefeatures 152. The induced tensile stress in the conductive features 152causes the conductive features 152 to warp to form a concave shape,which in turn causes one or more cracks formed in the RDL 140. Thecracks can propagate into the interconnection structure 120, leading todevice failure. To resolve this issue, the second passivation layer 146having a multi-layer stack is utilized. In some embodiments, the secondpassivation layer 146 includes a nitride layer having a thickness thatis at least 40 percent, such as from about 40 percent to about 80percent, of the total thickness of the second passivation layer 146. Insome embodiments, the second passivation layer 146 includes two nitridelayers. The second passivation layer 146 is described in detail below.

The second passivation layer 146 is a multi-layer stack to reduceformation of cracks in the RDL 140, confine the cracks within the secondpassivation layer 146, or both. As shown in FIG. 3A, in someembodiments, the second passivation layer 146 includes a firstpassivation sublayer 146A disposed on the first passivation layer 144and the conductive features 152, a second passivation sublayer 146Bdisposed on the first passivation sublayer 146A, and a third passivationsublayer 146C disposed on the second passivation sublayer 146B. One ormore of the first, second, third passivation sublayers 146A, 146B, 146Cmay be conformally formed by a conformal deposition process, such asatomic layer deposition (ALD). Each of the first passivation sublayer146A, second passivation sublayer 146B, and third passivation sublayer146C is made from a dielectric material, such as silicon oxide, siliconoxycarbide, one or more porous low-k dielectric materials, undopedsilica glass, borophosphosilicate glass, phosphosilicate glass, boronsilicate glass, silicon nitride, silicon oxynitride, silicon oxycarbonnitride, high density plasma oxide formed by HDP-CVD process or othersuitable processes, spin on glass, polyimide, other suitable materials,or a combination thereof. The adjacent passivation sublayers arefabricated from different dielectric materials. At least one of thefirst, second, and third passivation sublayers 146A, 146B, 146C is madefrom a nitride, such as silicon nitride, aluminum nitride, titaniumnitride, or tantalum nitride. The nitride-based passivation sublayer hasone or more of the following properties: Young's modulus greater than150 GPa, such as from about 150 GPa to about 350 GPa, fracture toughnessgreater than 3 MPa·m^(1/2), such as from about 3 MPa·m^(1/2) to about 7MPa·m^(1/2), or compressive stress greater than −1E9 dyne/cm², such asfrom about −1E9 dyne/cm² to about −3.5E10 dyne/cm². These properties arereferred to as the crack-reducing properties in this disclosure. In oneexample, one of the first, second, and third passivation sublayers 146A,146B, 146C is made from silicon nitride, which has all thecrack-reducing properties mentioned above.

In some embodiments, one of the first, second, and third passivationsublayers 146A, 146B, 146C is made from a nitride, and the nitride-basedpassivation sublayer has a thickness that is at least 40 percent, suchas from about 40 percent to about 80 percent, of the total thickness ofthe second passivation layer 146. The nitride-based passivation sublayerhaving at least one of the crack-reducing properties and a thicknessranging from about 40 percent to about 80 percent of the total thicknessof the second passivation layer 146 can reduce the formation of cracksin the passivation layer 146 and/or confine the cracks within thepassivation layer 146 by reducing the tensile stress of the conductivefeature 152. In one aspect, the nitride-based passivation sublayer has athickness greater than or equal to 1000 nm, such as from about 1000 nmto about 2000 nm. In some embodiments, the first passivation sublayer146A is made from undoped silica glass and has a thickness T3 rangingfrom about 100 nm to about 500 nm, the second passivation sublayer 146Bis made from high density plasma oxide and has a thickness T4 rangingfrom about 1000 nm to about 2000 nm, and the third passivation sublayer146C is made from silicon nitride and has a thickness T5 greater than orequal to 1000 nm, such as from about 1000 nm to about 2000 nm. In oneexample, the total thickness of the second passivation layer 146 isabout 2300 nm, and the third passivation sublayer 146C has a thicknessof about 1000 nm, which is about 43 percent of the total thickness ofthe second passivation layer 146. In some embodiments, with the thirdpassivation sublayer 146C being made from silicon nitride and having athickness at least 40 percent of the total thickness of the secondpassivation layer 146, it has been observed that the tensile stress inthe conductive feature 152 disposed below the second passivation layer146 was decreased by 15 percent to 25 percent, and the device failurerate decreased from 13 percent to five percent, compared to conventionalpassivation layer.

In some embodiments, two of the first, second, and third passivationsublayers 146A, 146B, 146C are made from a nitride having at least onecrack-reducing properties. The two nitride-based passivation sublayersmay be made from the same nitride material or different nitridematerials. In some embodiments, the two nitride-based passivationsublayers are separated by one or more passivation sublayers. Forexample, the first passivation sublayer 146A is made from siliconnitride and has the thickness T3 ranging from about 300 nm to about 1000nm, the second passivation sublayer 146B is made from undoped silicaglass and has the thickness T4 ranging from about 100 nm to about 500nm, and the third passivation sublayer 146C is made from silicon nitrideand has the thickness T5 ranging from about 300 nm to about 1000 nm. Inone example, the thickness T5 of the third passivation sublayer 146C isgreater than the thickness T3 of the first passivation sublayer 146A.

FIG. 3B is a cross-sectional side view of the RDL 140 at one stageduring fabrication of the semiconductor device structure 100 of FIG. 1,in accordance with some embodiments. As shown in FIG. 3B, in someembodiments, the RDL 140 includes the first passivation layer 144 havingthe first passivation sublayer 144A and the second passivation sublayer144B, the conductive features 150, the conductive features 152, and thesecond passivation layer 146. In some embodiments, the secondpassivation layer 146 includes the first passivation sublayer 146A, thesecond passivation sublayer 146B, the third passivation sublayer 146C, afourth passivation sublayer 146D disposed on the third passivationsublayer 146C, and a fifth passivation sublayer 146E disposed on thefourth passivation sublayer 146D. One or both of the fourth and fifthpassivation sublayers 146D, 146E may be conformally formed by aconformal deposition process, such as ALD. Each of the passivationsublayers 146D-146E is made from a dielectric material, such as siliconoxide, silicon oxycarbide, one or more porous low-k dielectricmaterials, undoped silica glass, borophosphosilicate glass,phosphosilicate glass, boron silicate glass, silicon nitride, siliconoxynitride, silicon oxycarbon nitride, high density plasma oxide formedby HDP-CVD process or other suitable processes, spin on glass, orpolyimide, other suitable materials, or a combination thereof. At leastone passivation sublayer of the second passivation layer 146 is madefrom a nitride having at least one of the crack-reducing properties, andthe nitride-based passivation sublayer has a thickness that is at least40 percent of the total thickness of the second passivation layer 146.The adjacent passivation sublayers are made from different dielectricmaterials. For example, the first passivation sublayer 146A is made froma material different from the second passivation sublayer 146B, thethird passivation sublayer 146C is made from a material different fromthe second passivation sublayer 146B, the fourth passivation sublayer146D is made from a material different from the third passivationsublayer 146C, and the fifth passivation sublayer 146E is made from amaterial different from the fourth passivation sublayer 146D. In someaspects, passivation sublayers not adjacent to each other may be madefrom the same material.

In some embodiments, one of the first, second, third, fourth, and fifthpassivation sublayers 146A, 146B, 146C, 146D, 146E is made from anitride having at least one of the crack-reducing properties, and thenitride-based passivation sublayer has a thickness that is at least 40percent, such as from about 40 percent to about 80 percent, of the totalthickness of the second passivation layer 146. In another embodiment, atleast two of the first, second, third, fourth, and fifth passivationsublayers 146A, 146B, 146C, 146D, 146E are fabricated from a nitridehaving at least one of the crack-reducing properties. The at least twonitride-based passivation sublayers may be made from the same nitridematerial or different nitride materials. In some embodiments, the atleast two nitride-based passivation sublayers each has a thicknessranging from about 300 nm to about 1000 nm. With two nitride-basedpassivation sublayers each having at least one of the crack-reducingproperties and a thickness ranging from about 300 nm to about 1000 nm,the second passivation layer 146 can reduce the formation of cracks inthe passivation layer 146 and/or confine the cracks within thepassivation layer 146 by reducing the tensile stress of the conductivefeature 152. In one aspect, the two nitride-based passivation sublayersare separated by one or more passivation sublayers. For example, thefirst passivation sublayer 146A is made from undoped silica glass andhas the thickness T3 ranging from about 100 nm to about 500 nm, thesecond passivation sublayer 146B is made from high density plasma oxideand has the thickness T4 ranging from about 1000 nm to about 2000 nm,the third passivation sublayer 146C is made from silicon nitride and hasthe thickness T5 ranging from about 300 nm to about 1000 nm, the fourthpassivation sublayer 146D is made from undoped silica glass and has athickness T6 less than about 100 nm, such as from about 50 nm to about100 nm, and the fifth passivation sublayer 146E is made from siliconnitride and has a thickness T7 ranging from about 300 nm to about 1000nm. In one aspect, the thickness T7 of the fifth passivation sublayer146E is greater than the thickness T5 of the third passivation sublayer146C. In some embodiments, with the third and fifth passivationsublayers 146C, 146E being made from silicon nitride and each having athickness ranging from about 300 nm to about 1000 nm, tensile stress inthe conductive feature 152 disposed below the second passivation layer146 is decreased by 15 percent to 60 percent, and the device failurerate decreased from 13 percent to zero percent, compared to conventionalpassivation layer.

The second passivation layer 146 having the passivation sublayers146A-146C (e.g., embodiments shown in FIG. 3A) or passivation sublayers146A-146E (e.g., embodiments shown in FIG. 3B) reduces cracks formed inthe second passivation layer 146 and/or confines the cracks within thesecond passivation layer 146. The second passivation layer 146 may beutilized in the RDL 140, as described herein. The second passivationlayer 146 may be utilized in other structures where cracks can form andpropagate due to mismatch in coefficient of thermal expansion.

FIG. 4 is a flowchart of a method 400 for fabricating the RDL 140 of thesemiconductor device structure 100 of FIG. 1, in accordance with someembodiments. FIGS. 5A-5I illustrate cross-sectional side views of theRDL 140 during various fabrication stages of the method 400 of FIG. 4,in accordance with some embodiments. The RDL 140 and the method 400making the same are collectively described with reference to FIGS. 4 and5A-5I. As shown in FIGS. 4 and 5A, the method 400 starts at operation402 to form a first dielectric layer 504 on a substrate 500. Thesubstrate 500 may be the substrate 102 with the interconnectionstructure 120 disposed thereon, as shown in FIG. 1. The substrate 500includes a dielectric material 502 and one or more conductive features501. The dielectric material 502 may be the ILD 122 and the conductivefeatures 501 may be the conductive features 126, as shown in FIG. 1.Each conductive feature 501 has a conductive surface 503, and eachdielectric material 502 has a dielectric surface 505. The firstdielectric layer 504 may be formed on the conductive surfaces 503 andthe dielectric surfaces 505. The first dielectric layer 504 may bedeposited by any suitable deposition method, such as ALD, CVD, PECVD,HDP-CVD, or spin-on coating. The first dielectric layer 504 may be thefirst passivation sublayer 144A of the first passivation layer 144, asshown in FIG. 3B.

At operation 404, a second dielectric layer 506 is formed on the firstdielectric layer 504, as shown in FIG. 5B. The second dielectric layer506 may be deposited by any suitable deposition method, such as ALD,CVD, PECVD, HDP-CVD, or spin-on coating. The second dielectric layer 506may be the second passivation sublayer 144B of the first passivationlayer 144, as shown in FIG. 3B. Next, at operation 406, the first andsecond dielectric layers 504, 506 are patterned, and openings 507 areformed in the first and second dielectric layers 504, 506, as shown inFIG. 5C. The patterning of the first and second dielectric layers 504,506 may include forming a mask on the second dielectric layer 506 andremove portions of the mask located over the conductive features 501.The openings 507 may be formed by any suitable removal process, such asdry etching. The conductive surfaces 503 are exposed through theopenings 507, and the dielectric surfaces 505 remain covered by thefirst and second dielectric layers 504, 506.

At operation 408, first plurality of conductive features 508 is formedin the openings 507, as shown in FIG. 5D. The conductive features 508may be the conductive features 150 shown in FIG. 3B. The conductivefeatures 508 may be formed by any suitable deposition method, such asPVD or electro-chemical plating (ECP). A CMP process may be performedafter forming the conductive features 508 to remove any conductivematerial formed on the second dielectric layer 506. Next, at operation410, a second plurality of conductive features 510 is formed on theconductive features 508, as shown in FIG. 5D. Each conductive feature510 may be formed on a corresponding conductive feature 508. Theconductive features 510 may be the conductive features 152 shown in FIG.3B. The conductive features 510 may be formed by any suitable depositionmethod, such as PVD or ECP. In some embodiments, the conductive features508, 510 are formed by a single deposition process. For example, thedeposition process may be performed to fill the openings 507 with aconductive material and to form a layer of conductive material on thesecond dielectric layer 506, followed by patterning the layer ofconductive material and removing portions of the conductive material toform conductive features 510.

At operation 412, a third dielectric layer 512 is formed on theconductive features 510 and the second dielectric layer 506, as shown inFIG. 5E. The third dielectric layer 512 may be conformally formed. Thethird dielectric layer 512 may be deposited by any suitable depositionmethod, such as ALD, CVD, PECVD, HDP-CVD, or spin-on coating. The thirddielectric layer 512 may be the first passivation sublayer 146A of thesecond passivation layer 146, as shown in FIG. 3B. Next, at operation414, a fourth dielectric layer 514 is formed on the third dielectriclayer 512, as shown in FIG. 5F. The fourth dielectric layer 514 may beconformally formed. The fourth dielectric layer 514 may be deposited byany suitable deposition method, such as ALD, CVD, PECVD, HDP-CVD, orspin-on coating. The fourth dielectric layer 514 may be the secondpassivation sublayer 146B of the second passivation layer 146, as shownin FIG. 3B.

At operation 416, a fifth dielectric layer 516 is formed on the fourthdielectric layer 514, as shown in FIG. 5G. The fifth dielectric layer516 may be conformally formed. The fifth dielectric layer 516 may bedeposited by any suitable deposition method, such as ALD, CVD, PECVD,HDP-CVD, or spin-on coating. The fifth dielectric layer 516 may be thethird passivation sublayer 146C of the second passivation layer 146, asshown in FIG. 3B. In some embodiments, the fifth dielectric layer 516may be made from a nitride. For example, the fifth dielectric layer 516is made from silicon nitride and is deposited by a PECVD process. Anexemplary PECVD process may include flowing precursor gases andadditional gases into a process chamber. The precursor gases may be asilicon containing gas and a nitrogen containing gas. The siliconcontaining gas may include silane, disilane, trimethylsilyl (TMS),tris(dimethylamino)silane (TDMAS),bis(tertiary-butylamino)silane(BTBAS), dichlorosilane (DCS), orcombinations thereof. The nitrogen containing gas may include nitrogen,ammonia, or combinations thereof. Additional gases may include a carriergas and gases that can tune the properties of the silicon nitride layer.The carrier gas may be an inert gas, such as argon. The gases that cantune the properties of the silicon nitride layer may include hydrogengas, which may increase the compressive stress of the silicon nitridelayer. The silicon containing gas has a flow rate ranging from about 10standard cubic centimeter per minute (sccm) to about 200 sccm, thenitrogen containing gas has a flow rate ranging from about 50 sccm toabout 500 sccm, and the carrier gas has a flow rate ranging from about100 sccm to about 5000 sccm. The RF power may be at a frequency rangingfrom about 0.3 MHz to about 14 MHz, such as about 13.56 MHz, and the RFpower may range from about 10 Watts to about 5000 Watts. The chamberpressure may range from about 10 mTorr to about 15 Torr, and thesubstrate temperature may range from about 200 degrees Celsius to about700 degrees Celsius.

In some embodiments, the third dielectric layer 512 is the firstpassivation sublayer 146A, the fourth dielectric layer 514 is the secondpassivation sublayer 146B, the fifth dielectric layer 516 is the thirdpassivation sublayer 146C, as shown in FIG. 3A, and the fifth dielectriclayer 516 has a thickness that is at least 40 percent of the totalthickness of the third, fourth, and fifth dielectric layers 512, 514,516. Subsequent processes include patterning and removing portions ofthe third, fourth, fifth dielectric layer 512, 514, 516 to expose theconductive features 510, and forming the UBM layer 154 (FIG. 1) on theconductive features 510. In some embodiments, the fifth dielectric layer516 has a thickness ranging from about 300 nm to about 1000 nm, andadditional dielectric layers are formed on the fifth dielectric layer516.

Next, at operation 418, a sixth dielectric layer 518 is formed on thefifth dielectric layer 516, as shown in FIG. 5H. The sixth dielectriclayer 518 may be conformally formed. The sixth dielectric layer 518 maybe deposited by any suitable deposition method, such as ALD, CVD, PECVD,HDP-CVD, or spin-on coating. The sixth dielectric layer 518 may be thefourth passivation sublayer 146D of the second passivation layer 146, asshown in FIG. 3B.

At operation 420, a seventh dielectric layer 520 is formed on the sixthdielectric layer 518, as shown in FIG. 5I. The seventh dielectric layer520 may be conformally formed. The seventh dielectric layer 520 may bedeposited by any suitable deposition method, such as ALD, CVD, PECVD,HDP-CVD, or spin-on coating. The seventh dielectric layer 520 may be thefifth passivation sublayer 146E of the second passivation layer 146, asshown in FIG. 3B. In some embodiments, the seventh dielectric layer 520may be made from a nitride. In one embodiment, the seventh dielectriclayer 520 is made from silicon nitride and is deposited by the PECVDprocess described above. The seventh dielectric layer 520 has athickness ranging from about 300 nm to about 1000 nm. In someembodiments, the fifth and seventh dielectric layers 516, 520 are madefrom a nitride, such as silicon nitride, and the seventh dielectriclayer 520 is thicker than the fifth dielectric layer 516.

Because the second passivation layer 146 can reduce cracks formationand/or confine the cracks within the passivation layer 146, limitationson the dimensions and arrangements of conventional conductive featuresare expanded. FIG. 6A is a cross-sectional side view of the secondpassivation layer 146 over a plurality of conductive features, inaccordance with some embodiments. As shown in FIG. 6A, the conductivefeatures include a first level of conductive features 602A, 602B, 602C,602D. The conductive features 602A, 602B, 602C, 602D may be theconductive features 126 disposed in the interconnection structure 120,as shown in FIG. 1. The conductive feature 602A has a first width W1,and the conductive features 602B, 602C, 602D each has a second width W2.In some embodiments, the first width W1 is greater than the second widthW2. In some embodiments, the conductive features 602B, 602C, 602D havedifferent widths from each other. The conductive features 602A, 602B,602C, 602D may be formed by forming a conductive layer, patterning theconductive layer, and removing portions of the conductive layer. In someembodiments, the conductive features 602A, 602B, 602C, 602D have thesame thickness T8.

A second level of conductive features 604A, 604B, 604C, 604D is disposedover the conductive features 602A, 602B, 602C, 602D. The conductivefeatures 604A, 604B, 604C, 604D may be the conductive features 126disposed at the top of the interconnection structure 120, as shown inFIG. 1. Both levels of the conductive features 602A-602D and 604A-604Dmay be embedded in the ILD 122. In one embodiment, the conductivefeatures 604A, 604B, 604C, 604D are aligned with correspondingconductive features 602A, 602B, 602C, 602D. The conductive viasconnecting the two levels of conductive features 602A-602D and 604A-604Dare omitted for clarity. The conductive feature 604A may have the samewidth as or a different width from the width W1 of the conductivefeature 602A. The conductive features 604B, 604C, 604D may have the samewidth as or different widths from each other. In some embodiment, theconductive features 604B, 604C, 604D each has the width W2. Theconductive features 604A, 604B, 604C, 604D may be formed by forming aconductive layer, patterning the conductive layer, and removing portionsof the conductive layer. In one embodiment, the conductive features604A, 604B, 604C, 604D have the same thickness T9, and the thickness T9is greater than the thickness T8.

The first passivation layer 144 is disposed on the second level ofconductive features 604A-604D and the ILD 122, as shown in FIG. 6A. Athird level of conductive features 606A, 606B, 606C, 606D is disposed onthe first passivation layer 144 and over the conductive features 604A,604B, 604C, 604D. The conductive features 606A, 606B, 606C, 606D may bethe conductive features 152 disposed in the RDL 140, as shown in FIG. 1.In some embodiments, the conductive features 606A, 606B, 606C, 606D arealigned with corresponding conductive features 604A, 604B, 604C, 604D.The conductive feature 606A may have the same width as or a differentwidth from the width W1 of the conductive feature 602A. The conductivefeatures 606B, 606C, 606D may have the same width as or different widthsfrom each other. In some embodiments, the conductive features 606B,606C, 606D each has the width W2. The conductive features 606A, 606B,606C, 606D may be formed by forming a conductive layer, patterning theconductive layer, and removing portions of the conductive layer. In oneembodiment, the conductive features 606A, 606B, 606C, 606D have the samethickness T10, and the thickness T10 is greater than the thickness T9.

FIG. 6B is a top view of the plurality of the conductive features606A-606D of FIG. 6A, in accordance with some embodiments. In someembodiments, the conductive feature 606A is a bonding pad, and theconductive features 606B, 606C, 606D are conductive lines. As shown inFIG. 6B, the conductive feature 606A has a polygonal shape. In oneembodiment, the conductive feature 606A is rectangular and has aconstant width. In another embodiment, the conductive feature 606A isoctagonal and has a width that varies, as shown in FIG. 6B. Theconductive feature 606B is adjacent the conductive feature 606A and hasa polygonal shape, such as rectangular. In one embodiment, the distancebetween the conductive feature 606A and the conductive feature 606B isconstant. In another embodiment, the distance between the conductivefeature 606A and the conductive feature 606B varies. For example, thecenter portion of the conductive feature 606A is a distance D1 away fromthe conductive feature 606B, and the edge portions of the conductivefeature 606A is a distance D2 away from the conductive feature 606B.Depending on the shape of the conductive feature 606A and/or the shapeof the conductive feature 606B, the distance D1 may be greater or lessthan the distance D2.

In some embodiments, the conductive feature 606C is adjacent theconductive feature 606B and has a polygonal shape, such as rectangular.A distance D3 is between the conductive feature 606C and the conductivefeature 606B. In some embodiments, the distance D3 is less than thedistance D1, such as about half of the distance D1. The conductivefeature 606D is adjacent the conductive feature 606C and has a polygonalshape, such as rectangular. The conductive feature 606C and theconductive feature 606D may be spaced apart by the distance D3.

The present disclosure in various embodiments provides a passivationlayer 146 of a semiconductor device structure 100 and the method ofmaking the passivation layer 146. The passivation layer 146 is disposedon a conductive feature and a dielectric material. In one embodiment,the passivation layer 146 includes a plurality of dielectric layers, andat least one layer of the plurality of dielectric layers is made fromnitride and has at least one of the following properties: Young'smodulus greater than 150 GPa, such as from about 150 GPa to about 350GPa, fracture toughness greater than 3 MPa·m^(1/2), such as from about 3MPa·m^(1/2) to about 7 MPa·m^(1/2), or compressive stress greater than−1E9 dyne/cm², such as from about −1E9 dyne/cm² to about −3.5E10dyne/cm². The nitride-based dielectric layer of the passivation layer146 has a thickness that is at least 40 percent, such as from about 40percent to about 80 percent, of the total thickness of the passivationlayer 146. In another embodiment, at least two dielectric layers of thepassivation layer 146 are made from a nitride having at least one of theproperties mentioned above. Some embodiments may achieve advantages. Forexample, the passivation layer 146 reduces the formation of the cracksin the passivation layer 146 and/or confines the cracks within thepassivation layer 146 by reducing the tensile stress of the conductivefeature 152, such as a bonding pad, disposed therebelow.

An embodiment is a semiconductor device structure. The structureincludes a substrate having one or more devices formed thereon, one ormore bonding pads disposed over the substrate, and a first passivationlayer disposed over the one or more bonding pads. The first passivationlayer includes a first passivation sublayer having a first dielectricmaterial, a second passivation sublayer disposed over the firstpassivation sublayer, and the second passivation sublayer has a seconddielectric material different from the first dielectric material. Thefirst passivation layer further includes a third passivation sublayerdisposed over the second passivation sublayer, and the third passivationsublayer has a third dielectric material different from the seconddielectric material. At least two of the first, second, and thirdpassivation sublayers each includes a nitride.

Another embodiment is a semiconductor device structure. The structureincludes a substrate having one or more devices formed thereon, aninterconnection structure disposed on the substrate, one or more bondingpads disposed over the interconnection structure, and a firstpassivation layer disposed over the one or more bonding pads. The firstpassivation layer includes a first passivation sublayer having a firstdielectric material, a second passivation sublayer disposed over thefirst passivation sublayer, and the second passivation sublayer has asecond dielectric material different from the first dielectric material.The first passivation layer further includes a third passivationsublayer disposed over the second passivation sublayer, and the thirdpassivation sublayer has a third dielectric material different from thesecond dielectric material. At least one of the first, second, and thirdpassivation sublayers is a nitride layer having a thickness at least 40percent of a total thickness of the first passivation layer.

A further embodiment is a method. The method includes forming one ormore devices on a substrate, forming a first dielectric layer over theone or more devices, forming an opening in the first dielectric layer,forming a first conductive feature in the opening, forming a bonding padover the first conductive feature, and forming a second dielectric layeron the bonding pad and the first dielectric layer. The forming thesecond dielectric layer includes forming a first sublayer over thebonding pad and the first dielectric layer. The first sublayer includesa first material. The forming the second dielectric layer furtherincludes forming a second sublayer on the first sublayer, and the secondsublayer includes a second material different from the first material.The forming the second dielectric layer further includes forming a thirdsublayer on the second sublayer, and the third sublayer includes a thirdmaterial different from the second material. At least two of the first,second, and third sublayers each includes a nitride.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method for forming a semiconductor device structure, comprising:forming a bonding pad over a substrate; forming a dielectric layer onthe bonding pad, wherein the forming the dielectric layer comprises:depositing a first sublayer over the bonding pad, wherein the firstsublayer comprises a first material; depositing a second sublayer on thefirst sublayer, wherein the second sublayer comprises a second materialdifferent from the first material; and depositing a third sublayer onthe second sublayer, wherein the third sublayer comprises a thirdmaterial different from the second material, at least one of the first,second, and third materials is a nitride, and the first, second, orthird sublayer having the nitride has a thickness that is at least 40percent of a thickness of the dielectric layer.
 2. The method of claim1, wherein the nitride comprises silicon nitride, aluminum nitride,titanium nitride, or tantalum nitride.
 3. The method of claim 2, whereinthe nitride is silicon nitride.
 4. The method of claim 1, wherein thethird material is the silicon nitride.
 5. The method of claim 4, whereinthe third sublayer is formed by a plasma enhanced chemical vapordeposition (PECVD) process.
 6. The method of claim 5, wherein the PECVDprocess comprises flowing a silicon containing gas and a nitrogencontaining gas into a process chamber.
 7. The method of claim 6, whereinsilicon containing gas comprises silane, disilane, trimethylsilyl,tris(dimethylamino)silane, bis(tertiary-butylamino)silane, ordichlorosilane, and the nitrogen containing gas comprises nitrogen orammonia.
 8. The method of claim 6, wherein the silicon containing gas isflowed into the process chamber at a flow rate ranging from about 10sccm to about 200 sccm, and the nitrogen containing gas is flowed intothe process chamber at a flow rate ranging from about 50 sccm to about500 sccm.
 9. The method of claim 8, wherein a chamber pressure of thePECVD process ranges from about 10 mTorr to about 15 Ton, and asubstrate temperature of the PECVD process ranges from about 200 degreesCelsius to about 700 degrees Celsius.
 10. The method of claim 4, whereinthe forming the dielectric layer further comprises depositing a fourthsublayer on the third sublayer and depositing a fifth sublayer on thefourth sublayer.
 11. The method of claim 10, wherein the fourth sublayercomprises a fourth material different from the third material, and thefifth sublayer comprises a fifth material different from the fourthmaterial.
 12. The method of claim 11, wherein the first materialcomprises undoped silica glass, the second material comprises an oxideformed by a high density plasma chemical vapor deposition process, thefourth material comprises undoped silica glass, and the fifth materialcomprises silicon nitride.
 13. The method of claim 12, furthercomprising forming an under bump metallurgy layer in the dielectriclayer, wherein the under bump metallurgy layer is in contact with thebonding pad.
 14. A semiconductor device structure, comprising: asubstrate including one or more devices formed thereon; aninterconnection structure disposed on the substrate; one or more bondingpads disposed over the interconnection structure; and a firstpassivation layer disposed over the one or more bonding pads, whereinthe first passivation layer comprises: a first passivation sublayercomprising a first dielectric material; a second passivation sublayerdisposed over the first passivation sublayer, the second passivationsublayer comprising a second dielectric material different from thefirst dielectric material; and a third passivation sublayer disposedover the second passivation sublayer, the third passivation sublayercomprising a third dielectric material different from the seconddielectric material, wherein at least one of the first, second, andthird passivation sublayers is a nitride layer having a thickness atleast 40 percent of a total thickness of the first passivation layer.15. The semiconductor device structure of claim 14, wherein the thirdpassivation sublayer is silicon nitride having a thickness greater thanor equal to 1000 nm.
 16. The semiconductor device structure of claim 14,further comprising a second passivation layer, wherein the firstpassivation layer is disposed on the second passivation layer.
 17. Thesemiconductor device structure of claim 16, wherein the secondpassivation layer comprises: a fourth passivation sublayer disposed onthe interconnection structure; and a fifth passivation sublayer disposedon the fourth passivation sublayer.
 18. A method for forming asemiconductor device structure, comprising: forming one or more deviceson a substrate; forming a first dielectric layer over the one or moredevices; forming an opening in the first dielectric layer; forming afirst conductive feature in the opening; forming a bonding pad over thefirst conductive feature; and forming a second dielectric layer on thebonding pad and the first dielectric layer, wherein the forming thesecond dielectric layer comprises: forming a first sublayer over thebonding pad and the first dielectric layer, wherein the first sublayercomprises a first material; forming a second sublayer on the firstsublayer, wherein the second sublayer comprises a second materialdifferent from the first material; and forming a third sublayer on thesecond sublayer, wherein the third sublayer comprises a third materialdifferent from the second material, and at least two of the first,second, and third sublayers each comprises a nitride.
 19. The method ofclaim 18, wherein the third sublayer comprises silicon nitride and isformed by a plasma enhanced chemical vapor deposition process.
 20. Themethod of claim 19, wherein the forming the second dielectric layerfurther comprises: forming a fourth sublayer on the first sublayer onthe bonding pad and the first dielectric layer; and forming a fifthsublayer on the fourth sublayer, wherein the first sublayer is formed onthe fifth sublayer, and the first sublayer comprises silicon nitride.